A person's two inner-ear organs (one associated with the right-hand ear and the other associated with the left-hand ear) each include the labyrinth, a delicate membranous system of fluid passages that includes both the cochlea (which is part of the auditory system), and the vestibular system (which provides part of the sense of balance).
Each inner-ear includes a tympanic membrane (eardrum) that receives sounds from the environment and conducts the resulting vibrations to the cochlea via the three auditory ossicles (the tympanic membrane connects to the malleus (hammer), which articulates with the incus (anvil), which is attached to stapes (stirrup), which is attached to the membrane of the fenestra ovalis, the oval membrane between the middle ear and the vestibule of the inner ear). Inside the coiled cochlea is the Organ of Corti, which converts sound vibrations into nerve action potentials (NAPs) that convey auditory information to the person's brain. Different positions along the length of the Organ of Corti between the two spiral fluid paths of the cochlea are responsive to different sound frequencies. Thus, in order to provide good hearing to a person who has lost her or his sense of hearing, it would be desirable to increase the number of separate stimulation signals to different spiral ganglion cells in the cochlea, or other auditory neurons and nerves. When electrical stimulation is used to trigger auditory NAPs, the number of separate signals is limited because the electrical field is diffuse and each electrode will stimulate neighboring nerves to the nerve to which the stimulation is directed. Several of the related patent applications identified above describe the advantages of using optical stimulation to provide reliable triggering of the desired NAPs for a particular auditory nerve while reducing inadvertent stimulation of neighboring auditory nerves.
Each inner-ear also includes three semicircular canals and a vestibule, the region where the semicircular canals converge, and which is close to the cochlea (the hearing organ). The vestibular system also works with the visual system to keep objects in focus when the head is moving. In addition to sense-of-balance signals from the vestibular system, the person's eyes also provide signals used for balance, as do joint and muscle receptors and the cerebellum. A bundle of nerves carries NAP signals from the inner ear organs to the brain. The brain, specifically the vestibular nuclear complex, receives and analyzes the information from these systems, and generates signals that control a person's balance.
U.S. Pat. No. 7,225,028 issued to Della Santina et al. on May 29, 2007, and titled “Dual Cochlear/Vestibular Stimulator with Control Signals Derived from Motion and Speech Signals”, is incorporated herein by reference. Della Santina et al. describe a system for treating patients affected both by hearing loss and by balance disorders related to vestibular hypofunction and/or malfunction, which includes sensors of sound and head movement, processing circuitry, a power source, and an implantable electrical stimulator capable of stimulating areas of the cochlea and areas of the vestibular system.
As a convention used herein, a nerve will be defined as a collection of individual nerve fibers (i.e., axons) of individual nerve cells (neurons) that together form a set of nerve pathways (an integrated set of pathways for signal propagation within the nervous system). Subsets of the individual nerve fibers are each bundled into one of a plurality of fascicles that together form the nerve. Action potentials can occur in the axon portion of individual nerve cells. A series of individual nerve fibers that together form an integrated signal pathway starting at a sensory-receptor nerve ending and extending to the brain will be referred to as a sensory-nerve pathway, a series of individual nerve fibers that together form an integrated signal pathway starting at the brain and extending to a muscle cell will be referred to as a motor-nerve pathway. A sensory-nerve pathway that carries auditory signals will be referred to as an auditory-nerve pathway, and a sensory-nerve pathway that carries signals from the sense-of-balance organs (e.g., the vestibular organs of the inner ear, or perhaps the eyes) will be referred to as a sense-of-balance nerve pathway. The auditory nerve pathways extend from spiral ganglion nerves (ganglion of Corti) in the organ of Corti of the cochlea, through the auditory nerve (also called the cochlear nerve, which, when joined with the vestibular nerve (for the sense of balance) becomes part of the vestibulocochlear nerve (also called cranial nerve VIII)) that extends to the cochlear nucleus of the brainstem, midbrain and then to the auditory cortex.
Within each fascicle of a nerve, there will typically be a plurality of sensory-nerve pathways and a plurality of motor-nerve pathways, wherein the number of sensory-nerve pathways will typically be about fifteen times as many as the number of motor-nerve pathways. As well, a series of individual nerve fibers may together form an integrated pathway starting at one of various internal organs and ending in the brain, with then other series of individual nerve fibers together forming an integrated pathway starting at the brain and extending to some internal end organ (such as the digestive tract, the heart, or blood vessels) as part of the autonomic nervous system; and a series of individual nerve fibers may together form an integrated pathway within the brain referred to as a tract. As used herein, a nerve bundle or fascicle refers to a collection of nerve fibers that subserve a like function (e.g., a fascicle may support a plurality of different motor-nerve pathways and thus motor-control signals needed for the muscles for a hand grasp, for example; similarly the same and/or a nearby fascicle may support a plurality of corresponding sensory-nerve pathways and thus sensory signals that provide the brain with feedback for the hand grasp).
Applying an electrical signal across or into a neuron (nerve cell), or a nerve bundle or nerve, is one way to stimulate a nerve action potential (NAP), either in a single neuron (nerve cell), or in a plurality of neurons within a nerve bundle, or within a nerve (the combined signals of NAPs in a nerve bundle or nerve are referred to as a compound nerve action potential (CNAP)). Applying an optical signal (e.g., a short relatively high-power pulse of infrared (IR) laser light, for example at a signal wavelength about 1.9 microns) is another way to stimulate a NAP.
U.S. patent application Ser. No. 12/018,185 filed Jan. 22, 2008 by Mark P. Bendett and James S. Webb, titled “Hybrid Optical-Electrical Probes,” which is incorporated herein by reference in its entirety, describes an optical-signal vestibular-nerve stimulation device and method that provides different nerve stimulation signals to a plurality of different vestibular nerves, including at least some of the three semicircular canal nerves and the two otolith organ nerves. In some embodiments described in that patent application, balance conditions of the person are sensed by the implanted device, and based on the sensed balance conditions, varying infrared (IR) nerve-stimulation signals are sent to a plurality of the different vestibular nerves. Also described is a method that includes obtaining light from an optical source; transmitting the light through an optical fiber between a tissue of an animal and an optical transducer, and detecting electrical signals using conductors attached to the optical fiber. The application also describes an apparatus that includes an optical source, an optical transmission medium operatively coupled to the optical source and configured to transmit light from the optical source to respective nerves of each of one or more organs of an animal, an electrical amplifier, and an electrical transmission medium integral with the optical transmission medium and operatively coupled to the electrical amplifier, wherein the electrical transmission medium is configured to transmit an electrical signal from the respective nerves to the electrical amplifier.
One way to treat deafness or hearing loss in a person is to implant a cochlear-stimulation device (frequently called a cochlear implant) that senses sound in the environment (e.g., using a microphone) and then generates a combination of different electrical signals in different locations in the person's cochlear inner-ear structure. Because it is difficult to confine the electric field of each one of a large number of separate electrical signals, each intended for a particular one of a large number of separate nerve pathways, e.g., among those nerve pathways that extend in the bundle from the cochlea into the brain (using conventional stimulation devices it is possible to generate CNAP responses in perhaps only sixteen different nerve pathways (channels)), this conventional approach can provide only a crude representation of normal hearing.
U.S. Pat. No. 6,921,413 issued Jul. 26, 2005 to Mahadevan-Jansen et al., titled “Methods and devices for optical stimulation of neural tissues,” and U.S. Pat. No. 7,736,382, which issued Jun. 15, 2010 to Webb et al. titled “Apparatus for Optical Stimulation of Nerves and Other Animal Tissue,” are each incorporated herein by reference in their entirety. Both of these describe optical stimulation of nerves in general.
U.S. Patent Application Publication No. US 2006/0161227, of Walsh et al., titled “Apparatus and Methods for Optical Stimulation of the Auditory Nerve,” is incorporated herein by reference in its entirety. This application describes a cochlear implant placed in a cochlea of a living subject for stimulating the auditory system of the living subject, where the auditory system comprises auditory neurons. In one embodiment, the cochlear implant includes a plurality of light sources {Li}, placeable distal to the cochlea, each light source being operable independently and adapted for generating an optical energy, Ei, wherein i=1, . . . , N, and N is the number of the light sources, and delivering means placeable in the cochlea and optically coupled to the plurality of light sources, {Li}, such that in operation, the optical energies {Ei} generated by the plurality of light sources {Li} are delivered to target sites, {Gi}, of auditory neurons, respectively, wherein the target sites G1 and GN of auditory neurons are substantially proximate to the apical end and the basal end of the cochlea, respectively.
U.S. Pat. No. 4,596,992 to Hornbeck issued Jun. 24, 1986 “Linear spatial light modulator and printer”, is incorporated herein by reference in its entirety. Hornbeck describes linear spatial light modulator with two offset rows of pixels for slight overlap of images, and a printer system using such a spatial light modulator with dark field projection optics is disclosed. The pixels include electrostatically deflectable elements which all bend in the same direction to permit use of dark field projection. The addressing electrodes for the elements are beneath the reflecting surface and arranged perpendicular to the rows of pixels with half on each side of the rows. The printer uses a xerographic engine for conversion of modulated light into print, and an entire row is printed without any scanning.
U.S. Pat. No. 7,787,170 to Patel et al., which issued Aug. 31, 2010 titled “Micromirror array assembly with in-array pillars”, is incorporated herein by reference in its entirety. Patel et al. describe a microstructure device comprising multiple substrates with the components of the device formed on the substrates. In order to maintain uniformity of the gap between the substrates, a plurality of pillars is provided and distributed in the gap so as to prevent decrease of the gap size. The increase of the gap size can be prevented by bonding the pillars to the components of the microstructure. Alternatively, the increase of the gap size can be prevented by maintaining the pressure inside the gap below the pressure under which the microstructure will be in operation. Electrical contact of the substrates on which the micromirrors and electrodes are formed can be made through many ways, such as electrical contact areas, electrical contact pads and electrical contact springs.
U.S. Patent Application Publication 2010/0162109 to Chatterjee et al. published Jun. 24, 2010 titled “USER INTERFACE HAVING CHANGEABLE TOPOGRAPHY”, and is incorporated herein by reference. Chatterjee et al. describe a device having changeable topography. The device can have a shape-changeable surface that can selectively alter according to an input so as to provide changeable topography of the user interface. The surface can include individual nodes that can raise above or lower below the initial surface. Alternatively, the surface can include a shape changeable material that can change the shape of portions thereof into discrete shapes above or below the initial surface. Alternatively, the surface can include a deformable material that can deform portions thereof into discrete forms above or below the initial surface. The changeable topography can define different user interface layouts.
U.S. Pat. No. 7,797,029 titled “Auditory midbrain implant” issued Sep. 14, 2010 to Peter Gibson et al. is incorporated herein by reference. Gibson et al. describe an electrode array that is implantable within the inferior colliculus of the midbrain and/or other appropriate regions of the brain of an implantee and adapted to provide electrical stimulation thereto. The electrode array an elongate member having a plurality of electrodes mounted thereon in a longitudinal array. A delivery cannula for delivering the electrode array having two half-pipes is also described.
There is a need for improved devices for generating nerve-stimulating optical signals (and optionally electrical signals, in order to trigger a nerve action potential (NAP) using a lower amount of optical-signal power than would be needed using optical stimulation alone) and for delivering the optical signals (and optionally electrical signals) to specific tissue locations in a person for the purpose of triggering desired nerve action potentials and/or inhibiting undesired nerve action potentials. There is also a need for detailed designs for an optical-signal-based (e.g., in some embodiments, laser-based) cochlear-implant system in order to restore a sense of hearing in individuals with severely impaired hearing, or with an absence of hearing altogether. There is a need for efficacious apparatus and methods for optically, or optically and electrically, stimulating auditory nerve and/or brain tissue in a living animal in order to generate a nerve action potential (NAP) in one neuron (nerve cell), or in a plurality of neurons within a nerve bundle or nerve (where the combined individual NAPs form a compound nerve action potential, or CNAP), or similar physiological response in the animal. Optical or electrical-and-optical stimulation of neurons can provide more precision in terms of stimulating a particular nerve pathway than is possible using only electrical stimulation. In some embodiments, there is a need to dissipate and spread out the heat energy from the optical laser sources and the electrical driving circuitry.